SQL vs NoSQL
Relational databases like PostgreSQL use fixed tables and SQL, while NoSQL databases trade structure for flexibility.
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SQL vs NoSQL
A relational database stores data in tables with a defined schema, enforces relationships with keys, and uses SQL and joins.
NoSQL systems (document, key-value, graph, column) choose flexible schemas and often scale horizontally. PostgreSQL blurs the line with JSONB, so you can mix structured columns and flexible documents.
Note:
Use a relational database when data has clear relationships and you need transactions.
Example: SQL vs NoSQL
CREATE TABLE customers (id INTEGER PRIMARY KEY, name TEXT, city TEXT);
CREATE TABLE orders (id INTEGER PRIMARY KEY, customer_id INTEGER, total INTEGER);
INSERT INTO customers VALUES (1, 'Ada', 'London'), (2, 'Bob', 'Oslo');
INSERT INTO orders VALUES (10, 1, 50), (11, 1, 20), (12, 2, 75);
-- Relational: related data lives in separate tables and is combined with a JOIN
SELECT c.name, o.total FROM customers c JOIN orders o ON o.customer_id = c.id ORDER BY o.id;
-- Output:
-- name | total
-- Ada | 50
-- Ada | 20
-- Bob | 75Login to try C/C++/Java/PHP code in the editor
Related Topics
Common Mistakes
- Choosing NoSQL only because it is trendy
- Storing everything as JSON in a relational database
- Assuming SQL cannot scale
Chapter Summary
- SQL databases use tables, schemas and joins
- NoSQL trades structure for flexibility
- PostgreSQL supports JSONB too
- Choose by data shape and consistency needs
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